On Wednesday, Sens. Joe Lieberman (I-Conn.) and John Warner (R-Va.) introduced bipartisan climate legislation — America’s Climate Security Act — at long last bridging the acrimonious divide between Republicans and, um, independents. Democrats have all but made it tripartisan — Senate Environment Committee head Barbara Boxer (D-Calif.) was gushing in her praise. Observers expect political support to coalesce around the bill, with senators like Boxer and Bernie Sanders (I-Vt.) working to beef it up and coal-state senators working to dilute it. Environmental groups were divided. Corporate-cozy Environmental Defense sang the bill’s praises, but other groups noted that although the bill’s gotten stronger since a draft was released in August, it still has significant flaws. The legislation would create a carbon cap-and-trade system covering 75 percent of the economy (greens want more), aiming for reductions 70 percent below 2005 levels by 2050 (greens want more). Only 24 percent of the pollution permits are auctioned to polluters rather than given away for free (greens want more). And so on.